1. Field
The present disclosure is directed to launch, retrieval, and servicing of a hovering aircraft, especially in turbulent winds or onto an irregularly-moving platform, such as a ship in a rough sea. The present disclosure is especially suited to unmanned aircraft of a small size. It allows for a fully automated operations cycle, whereby the aircraft can be repeatedly launched, retrieved, serviced, and re-launched, without manual intervention at any point, and while requiring only modest accuracy in piloting.
2. Description of Prior Art
Hovering aircraft, be they helicopters, thrust-vectoring jets, “tail-sitters”, or other types, usually land by gently descending in free thrust-borne flight onto a landing surface, coming to rest on an undercarriage of wheels, skids, or legs. This elementary technique can be problematic in certain situations, as for example when targeting a small, windswept landing pad on a ship moving in a rough sea. The well-known Beartrap or RAST (Stewart & Baekken 1968) as well as the harpoon-and-grid system (Wolters & Reimering 1994) are used by helicopters to permit retrieval with acceptable safety in such conditions. These systems require an expensive and substantial plant in the landing area, as well as manual operations coordinated between helicopter and shipboard crew. Furthermore, the helicopter must carry a complete undercarriage in addition to the components necessary for capturing the retrieval apparatus.
Desirable improvements relative to such existing systems include: (a) simplification of base and onboard apparatus, and (b) automated rather than manual operation. Ideally, automation would encompass not only retrieval but also subsequent servicing and launch. This would be particularly desirable for an unmanned aircraft, whose operations cycle could then be made fully autonomous. Some experimental work toward this objective has been done for a hovering aircraft by Mullens et al. (2004), but with limited success even with light wind and a stationary base. McGeer and von Flotow (2010) and McGeer et al. (2010) have disclosed techniques which by contrast provide for fully automated retrieval and turnaround in calm or rough conditions. These techniques involve a tether lowered from the aircraft to be retrieved. The present disclosure similarly provides for fully automated handling in calm or rough conditions, but does not require a tether. The associated apparatus is simple, portable, and suitable for a small vessel or similarly confined base.